Polycrystalline diamond materials formed from coarse-sized diamond grains

ABSTRACT

PCD materials of this invention comprise diamond crystals that are bonded together with a catalyst/binder material. The PCD material is prepared by combining diamond grains with a catalyst/binder material either as a premixture or by infiltration during sintering. The PCD material comprises 15 percent by volume or less diamond grains sized 20 micrometers or less. The diamond grains are pressurized under elevated temperature conditions to form the desired PCD material. PCD materials of this invention can constitute the exclusive material phase of a PCD construction, or can form one or more material phase in a multi-phase material microstructure, wherein the multiple material phase can be arranged in an ordered/oriented or random fashion. PCD materials of this invention display improved properties of impact and fatigue resistance, and functional toughness, when used in complex wear environments, when compared to conventional PCs materials comprising intentionally added fine-sized diamond grains.

FIELD OF THE INVENTION

This invention relates to polycrystalline diamond constructions used forsubterranean drilling applications and, more particularly, topolycrystalline diamond constructions comprising polycrystalline diamondmaterials that are formed substantially exclusively from coarse-sizeddiamond grains, and that provide improved properties of functionaltoughness when compared to conventional polycrystalline diamondconstructions.

BACKGROUND OF THE INVENTION

Polycrystalline diamond (PCD) materials known in the art are formed fromdiamond grains or crystals and a ductile metal catalyst/binder, and aresynthesized by high temperature/high pressure processes. Such PCDmaterials are well known for their mechanical property of high wearresistance, making them a popular material choice for use in suchindustrial applications as cutting tools for machining, and subterraneanmining and drilling, where the mechanical property of wear resistance ishighly desired. In such applications, conventional PCD materials can beprovided in the form of a surface coating on, e.g., inserts used withcutting and drilling tools, to impart improved wear resistance thereto.

Traditionally, PCD inserts used in such applications are formed bycoating a suitable substrate material with one or more layers ofPCD-based material. Such inserts comprise a substrate, a PCD surfacelayer, and often one or more transition layers to improve the bondingbetween the exposed PCD surface layer and the underlying substratesupport layer. Substrates used in such insert applications arepreferably formed from a carbide material, e.g., tungsten carbide (WC)cemented with cobalt (WC—Co).

The coated layer or layers of PCD conventionally may comprise a metalbinder up to about 10 percent by volume. The metal binder is used tofacilitate intercrystalline bonding between diamond grains, and acts tobond the layers to each other and to the underlying substrate. Metalsconventionally employed as the binder are often selected from the groupincluding cobalt, iron, or nickel and/or mixtures or alloys thereof. Thebinder material can also include metals such as manganese, tantalum,chromium and/or mixtures or alloys thereof. The metal binder can beprovided in powder form as an ingredient for forming the PCD material,or can be drawn into the PCD material from the substrate material duringthe high temperature/high pressure processing.

The amount of binder material that is used to form PCD materialsrepresents a compromise between the desired material properties oftoughness and hardness/wear resistance. While a higher metal bindercontent typically increases the toughness of a resulting PCD material,higher metal content also decreases the PCD material hardness andcorresponding wear resistance. Thus, these inversely affected desiredproperties ultimately limit the flexibility of being able to provide PCDcoatings having desired levels of both wear resistance and toughness tomeet the service demands of particular applications. Additionally, whenvariables are selected to increase the wear resistance of the PCDmaterial, typically brittleness also increases, thereby reducing thetoughness of the PCD material.

Conventional PCD materials comprise a large amount of fine-sized diamondgrains or powder. Fine-sized diamond grains are intentionally used as araw material for making conventional PCD materials to increase thevolume fraction of diamond in the PCD material, which increases the wearresistance of the sintered PCD material. Conventional PCD materials caneither be formed exclusively from fine-sized diamond grains, or can beformed from a mixture of fine-sized diamond grains with coarse-sizeddiamond grains. In either case, however, such conventional PCD materialsrely on the intentional use of a defined proportion of fine-sizeddiamond grains to increase the hardness and overall wear resistance ofthe PCD material.

Generally, such conventional PCD materials exhibit properties ofextremely high hardness, high modulus, and high compressive strength,and provide a high degree of wear protection to a cutting or drillingelement. However, in more complex wear environments known to causeimpact and high-load fatigue, layers formed from such conventional PCDmaterials are known to fail by gross chipping and spalling. For example,drilling inserts coated with a conventional PCD layer can exhibitbrittleness that causes substantial problems in practical applications.The breakage and/or failure of conventional PCD materials in suchapplications is a result of the relatively low toughness of thematerial.

It is, therefore, desirable that PCD materials be developed that displayimproved properties of impact and fatigue resistance and functionaltoughness for use in complex wear environments, when compared toconventional PCD materials, while displaying acceptable wear resistancefor use in the same applications.

SUMMARY OF THE INVENTION

PCD materials constructed in accordance with principles of thisinvention contain diamond or diamond phases prepared by using diamondgrains sized 20 micrometers or greater, and comprise up to about 50percent by volume catalyst/binder material based on the total volume ofthe material. PCD materials are prepared by taking the diamond grainstarting material and forming it during a processing step into a greenpart. The green part is then subjected to high temperature/high pressuresintering to form the PCD material. During the processing step thevolume percent of diamond grains sized 20 micrometers or less isincreased. Post-sintered PCD materials of this invention aresubstantially free of fine-sized diamond grains in that they comprise 15percent by volume or less diamond grains sized 20 micrometers or less.

PCD materials of this invention can constitute the exclusive materialphase of a PCD construction, or can form one or more material phase of amulti-phase material microstructure, wherein the multiple materialphases can be arranged in an ordered/oriented or random fashion. PCDmaterials of this invention display improved properties of impact andfatigue resistance and functional toughness when used in complex wearenvironments, when compared to conventional PCD materials comprisingfine-sized diamond grains, while displaying acceptable wear resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome appreciated as the same becomes better understood with referenceto the specification, claims and drawings wherein:

FIG. 1 is a schematic photomicrograph of a portion of a polycrystallinediamond material prepared according to principles of this invention;

FIG. 2 is a schematic perspective side view of an insert comprising apolycrystalline diamond material of this invention;

FIG. 3 is a perspective side view of a roller cone drill bit comprisinga number of the inserts of FIG. 2; and

FIG. 4 graphically illustrates the probability of failure for rock bitinserts formed from PCD materials of this invention as compared to thoseformed from conventional PCD materials.

DETAILED DESCRIPTION

As used in this specification, the term polycrystalline diamond, alongwith its abbreviation “PCD,” refers to the material that is produced bysubjecting individual diamond crystals or grains to sufficiently highpressure and high temperature that intercrystalline bonding occursbetween adjacent diamond crystals to form a network of diamondcrystal-to-diamond crystal bonding. Polycrystalline diamond (PCD)materials of this invention are formed from a distribution ofsubstantially exclusively coarse-sized diamond grains that are generallybonded together through the use of a catalyst material. PCD materials ofthis invention provide improved properties of impact resistance, fatigueresistance, and functional toughness, while maintaining an acceptabledegree of wear resistance, when compared to conventional PCD materialsprepared from the intentional use of fine-sized diamond grains.

FIG. 1 illustrates a microstructure of a PCD material 10 of thisinvention comprising a plurality of diamond grains 12 that are bonded toone another. A catalyst/binder material 14, e.g., cobalt, is used tofacilitate the diamond-to-diamond bonding that develops during thesintering process into a diamond crystal bonded network. Thecatalyst/binder material used to facilitate diamond-to-diamond bondingcan be provided generally in two ways. The catalyst/binder can beprovided in the form of a raw material powder that is pre-mixed with thediamond grains or grit prior to sintering. Alternatively, thecatalyst/binder can be provided by infiltration into the diamondmaterial (during high temperature/high pressure processing) from anunderlying substrate material that the final PCD material is to bebonded to.

After the catalyst/binder material has facilitated the diamondcrystal-to-diamond crystal bonding, and the final diamond part iscomplete, the catalyst/binder material is generally distributedthroughout the diamond network. Although the catalyst/binder materialcould be leached out of the diamond network to provide a “thermallystable” structure, it is typically left in to provide some toughness andadditional diamond crystal bonding support.

In an example embodiment, diamond grains used to form the PCD materialdiamond phase have a grain size of greater than about 20 micrometers,and preferably in the range of from about 30 to 90 micrometers. Diamondgrains sized greater than about 20 micrometers are referred to as“coarse-sized” diamond grains in this description for purposes ofdistinguishing the grains from smaller sized diamond grains or “fines”that are intentionally used for preparing those conventional PCDmaterials discussed above.

It is desired that PCD materials of this invention be formed by usingsubstantially exclusively coarse-sized diamond grains, as it has beendiscovered that such use produces a final PCD product in roller-conerockbits that displays improved properties of impact resistance andfunctional toughness when compared to conventional PCD materials formedby the intentional use of some amount of fine-sized diamond grains.While not wishing to be bound by a particular theory or mechanism, theresultant improvement in impact resistance and functional toughness isbelieved to be due to mechanisms of crack deflection and crack bridging.

While PCD materials of this invention are referred to as being formedsubstantially exclusively from coarse-grained diamond grains, it is tobe understood that most post-sintered PCD materials of this inventionwill have some residual amount of small or fine-sized diamond grains (onthe order of about 15 percent by volume or less). Although it is thepractice of this invention to not intentionally use diamond grainshaving a grain size of 20 micrometers or less, the presence of a certainamount of residual fines in the diamond grain raw material may beunavoidable.

For example, in an example embodiment, a diamond grain product usefulfor forming PCD materials of this invention has a grain size of fromabout 36 to 54 micrometers, and can have up to about 10 percent byvolume, and preferably less than about 5 percent by volume, residualdiamond fines of 20 micrometers in size or smaller. This presence ofthis amount of fines in the otherwise coarse diamond grain product isbelieved to be unintentional and possibly unavoidably related to theprocess of packaging, transporting and otherwise handling the diamondgrain product. This amount of unavoidable diamond fines in the diamondgrain product does not have any appreciable effect on diminishing thedesired improvement of impact resistance for the PCD material.

While it is the intent of this invention to use diamond grains that donot include intentionally added residual fines, it is to be understoodthat diamond grain materials having an acceptable amount of residualfines, whether present unintentionally or intentionally, can be used toprepare PCD materials of this invention and, thus are intended to bewithin the scope of this invention.

Residual diamond fines can also be introduced into the coarse-sizeddiamond powder during processing. For example, diamond fines can beproduced via the process of making the desired raw diamond powder bypowder milling and tape casting process. Additionally, various powdercompaction methods, up to and including high temperature/high pressuresintering, can create unwanted diamond fines. In an example embodiment,using the same diamond powder product described above (comprisingdiamond grains having a size of from 36 to 54 micrometers), the processof ball milling can increase the volume fraction of diamond finesinitially in the diamond grain product from approximately 2.5 percent toapproximately 25 percent. Further processing of the ball milled product,in the form of tape casting, can increase the volume fraction of diamondfines from approximately 25 percent to 42 percent based on the totalvolume of the material.

Since the creation of diamond fines are a largely unavoidableconsequence of the steps of processing diamond grains prior tosintering, unless such processing steps can be controlled, it isimportant that the amount of diamond fines in the starting diamond grainproduct be controlled to the desired maximum discussed above. Thecontrol of diamond grain size, and related use of substantiallycoarse-sized diamond grains, is important to provide post sintered PCDmaterials having desired improved properties of impact resistance andtoughness while retaining a sufficient level of wear resistance for use,e.g., as rock bit inserts, in particular subterranean drillingapplications. For example, use of substantially coarse-sized diamondgrains produces a post sintered PCD material having 15 percent by volumeor less diamond fines, thereby providing a material microstructurecapable of providing the above-discussed desired mix of performanceproperties.

Since the amount of diamond fines present in the diamond grain product,used to form PCD materials of this invention, can be controlled bychoice of raw material and method of processing, it is to be understoodthat one or both can be manipulated within the scope of this inventionto provide the desired control over diamond fines present in thepre-sintered PCD material.

It is, therefore, to be understood that although the maximum amount offine-sized diamond grains, used to prepare PCD materials of thisinvention, is carefully controlled, up to about 15 percent by volumediamond fines may be present in the sintered microstructure of thisinvention from the sources discussed above. As mentioned above, thepresence of up to about 15 percent by volume diamond fines in the postsintered PCD material provides a desired degree of impact resistance,toughness, and wear resistance for some applications. The exact amountof diamond fines present in PCD materials of this invention will dependon the particular application. For example, a PCD material comprisingapproximately 10 percent by volume diamond fines sized 20 micrometers orless can be well suited for use as a wear surface on a rock bit insert.

Accordingly, for purposes of distinguishing PCD materials of thisinvention from conventional PCD materials formed from the intentionaluse of fine-sized diamond grains, post sintered PCD materials of thisinvention are referred to as either being: (1) substantially free fromdiamond grains having a grain size of 20 micrometers or less; and/or (2)being prepared substantially exclusively from coarse-sized diamondgrains of greater than 20 micrometers.

PCD materials formed without controlling the maximum amount offine-sized diamond grains sized 20 micrometers or less, withoutadditional process and/or material composition enhancements, will nothave an amount of course-sized diamond grains present in the sinteredmicrostructure to provide a sufficient increase in functional toughnessover conventional PCD that is suitable for use of the final PCD productin certain extreme wear applications, e.g., as on a working surface of asubterranean drill bit.

The properties of toughness and wear resistance are considered to be themost important properties of PCD, and they are inversely related to oneanother, i.e., as one of the properties is improved, the other isreduced. As the diamond grain size used to form PCD materials increases,toughness typically increases and wear resistance typically decreases.Thus, maximum diamond grain size used to form PCD materials isdetermined by the toughness and wear resistance requirement called forby a particular PCD material application.

In the example application of PCD inserts installed on a petroleumroller-cone rock bit, wear of the PCD insert is not a current failuremode. Rather, the current failure mode is diamond chipping and spallingdue to fatigue and impact. The exact amount of wear resistance that canbe sacrificed to increase toughness and impact resistance has not beenestablished. Accordingly the maximum diamond grain size beneficial tooverall PCD insert performance is unknown at this time.

Formations drilled by rock bits vary considerably in terms of hardness,strength and abrasiveness. Therefore, it is to be understood that thelarge diamond grain size useful for forming PCD inserts used in rockbits will vary according to the formations being drilled to optimizeoverall performance. In a preferred embodiment, PCD materials of thisinvention used to form inserts for a rotary-cone rock bit are formed byusing diamond grains having a grain size in the range of from about 35to 55 micrometers.

The catalyst/binder material 14 can be selected from those bindermaterials/metals used to form conventional PCD materials such as Co, Ni,Fe, and mixtures and alloys thereof, as well as materials known to thoseskilled in the art. As discussed above, the properties of toughness andwear resistance of the PCD material are inversely related to oneanother, and are dependent on the relative amounts of catalyst/bindermaterial and diamond grains that are used. The presence of diamondgrains, and related diamond-to-diamond bonding, is necessary to providedesired properties of high strength and wear resistance to the PCDmaterial. However, too many diamond grains or excessive diamond bondingin the PCD material can produce low chipping resistance.

The presence of the catalyst/binder material in the PCD material canhelp to improve chipping resistance, but can adversely impact PCDmaterial properties of high strength and wear resistance. Therefore, theamount of catalyst/binder material that is used to form the PCD materialis preferably that amount that provides a desired improvement inchipping resistance without significantly impacting strength and wearresistance.

Cobalt (Co) is a preferred catalyst/binder material. PCD materials ofthis invention are formed using up to about 50 percent by volume of thecatalyst/binder material based on the total volume of the material.Using more than about 50 percent by volume of the catalyst/bindermaterial will provide a PCD material having properties of hardness andwear resistance that may not be sufficient for use in extreme workingenvironments, e.g., as a working surface on a subterranean drill bit, asthe high amount of catalyst/binder material will significantly reducethe overall amount of diamond-to-diamond bonding, as well as reduce theamount of diamond crystals, which significantly reduces the wearresistance of the PCD In a preferred embodiment, PCD materials of thisinvention comprise in the range of from 50 to 95 percent by volume ofthe coarse-sized diamond grains based on the total volume of thematerial.

Cobalt is provided in the form of powder having a grain size in therange of from about one to three micrometers. Using a Co catalyst/bindermaterial having a grain size within this range is desired because itminimizes residual voids in the microstructure. In an exampleembodiment, a PCD material is prepared according to this invention byusing approximately ten percent by volume Co as a premix material, i.e.,as a material that is combined with the diamond powder before sintering.Alternatively, the catalyst/binder material can be provided to thediamond powder by infiltration from a binder-containing substratematerial during the sintering process.

PCD materials of this invention are initially formed from a mixture ofdiamond grains and catalyst/binder powder that is formed into the shapeof a desired part, and that can be sintered by conventionalhigh-temperature high-pressure (HT/HP) process to form a desired PCDconstruction. Pre-sintered parts are formed by combining diamond grainsor grit having the above-described coarse grain size, with a suitablecatalyst/binder material, e.g., Co, in the desired proportions. Thediamond grains and catalyst/binder material are thoroughly mixedtogether by conventional method and are formed into a desired shape foruse with the final application product. For example, when used as aworking surface on a subterranean drill bit insert, the pre-sinteredpart can be formed into a shape that will cover a surface portion of aninsert substrate formed, e.g., from tungsten carbide-cobalt.Alternatively, if desired, the entire part can be formed from the PCDmaterial. The so-formed pre-sintered part is sintered by HT/HP processfor diamond synthesis. The sintered product contains the PCD material ofthis invention.

PCD materials, and PCD products formed therefrom, prepared according tothe principles of this invention will become better understood andappreciated with reference to the following example:

EXAMPLE

Diamond grains having a grain size of approximately 36 to 54 micrometerswere mixed with Co powder having an approximate grain size of about twomicrometers. The distribution of diamond grain sizes for the 36 to 54micrometer diamond grain powder was as follows: approximately 50 percentby volume 43 to 47 micrometer diamond grains; and approximately 90percent by volume less than or equal to 60 micrometer diamond grains.The mixture comprised approximately 90 percent by volume diamond grainsand the remaining amount Co. The mixture was prepared for forming aninsert used with a rotary-cone rock bit, according to conventional knownpractices and comprised less than about 15 percent by weightunintentionally present and unavoidable diamond fines having a grainsize of 20 micrometers or less. A pre-sintered part was formed from themixture. The pre-sintered part was sintered according to conventionalHT/HP parameters and produced a PCD material having a microstructurecomprising 15 percent by volume or less fine-sized diamond grains basedon the total volume of the material.

PCD constructions, formed from PCD materials of this invention, can havea material microstructure consisting exclusively of the PCD materialitself, i.e., the entire microstructure can be a homogeneous arrangementof the diamond crystals bonded together with a catalyst/binder material(as illustrated in FIG. 1). PCD constructions, formed from PCD materialsof this invention, can also have a material microstructure comprisingtwo or more material phases where the PCD materials of this invention isat least one of the material phases. Further, the two or more materialphases can be arranged within the microstructure in either a random orordered/oriented fashion.

An example PCD construction comprising the PCD material of thisinvention as one material phase, e.g., a hard phase, in an orientedmulti-phase material microstructure is described in U.S. Pat. No.6,063,502, which is incorporated herein by reference, comprising anordered/oriented arrangement of a first material phase of the PCDmaterial, and a second material phase of another material. An examplePCD construction comprising the PCD material of this invention as onematerial phase in a randomly arranged multi-phase materialmicrostructure can be one including the PCD material as a first hardmaterial phase that is randomly distributed within a second continuousmaterial phase of a second material, e.g., a catalyst/binder materialsuch as WC—Co and the like. It is to be understood that these are onlybut a few examples of how PCD materials of this invention can be used toform PCD constructions having both an ordered/oriented and randomlyarranged multi-phase material microstructure. It is, therefore, to beunderstood that many other example uses of PCD materials to form suchmulti-phase PCD constructions is both possible and is intended to bewithin the scope of this invention.

PCD carbide composites of this invention can be used to form wear andcutting components in earth-boring tools such as roller conebitscommonly used in the mining and petroleum drilling industry. PCDmaterials can be used to form a wear surface in such applications in theform of one or more substrate coating layers, or can be used to form theentire component itself.

FIG. 2, for example, illustrates a mining or petroleum drill bit insert24 that is either formed entirely from or that has a working surface 25comprising the PCD material of this invention. Again, it is to beunderstood that the PCD material can be the only material phase of thisand the following example PCD constructions, or can be one or morephases of an ordered/oriented or random multi-phase materialmicrostructure. Referring to FIG. 3, such an insert 24 can be used witha roller cone drill bit 26, comprising a body 28 having three legs 30,and a cutter cone 32 mounted on a lower end of each leg. The inserts 24are provided along the surfaces of the cutter cone 32 for bearing on arock formation being drilled.

PCD materials of this invention, formed by using substantiallyexclusively coarse-sized diamond grains, display improved properties offunctional toughness when compared to conventional PCD materials formedby intentionally using a fine-sized diamond grain component. FIG. 4illustrates graphically the reduced probability failure that rock bitinserts formed from PCD materials of this invention display whencompared to conventional PCD materials. Specifically, FIG. 4 illustratesthat the probability of failure for rock bit inserts comprising asurface formed from the PCD material of this invention is much less at agiven impact failure height than that of a rock bit insert comprising asurface formed from a conventional PCD material. For example, at animpact failure height of approximately 75 inches, the probability offailure is reduced from approximately 80 percent (for a rock bit insertcomprising a conventional PCD material) to approximately 20 percent (foran equally-sized rock bit insert comprising the PCD material of thisinvention), which represents a substantial improvement in functionaltoughness.

Although, limited embodiments of PCD materials, methods of making thesame, and applications for the same, have been described and illustratedherein, many modifications and variations will be apparent to thoseskilled in the art. Additionally, although PCD materials of thisinvention have been described as being useful to form a working surfaceon a particular substrate, it is to be understood within the scope ofthis invention that PCD materials of this invention can also be used toform multiple-layer structures, or to form the entire insert itself,thus not requiring a substrate. Accordingly, it is to be understood thatwithin the scope of the appended claims, PCD materials according toprinciples of this invention may be embodied other than as specificallydescribed herein.

1. A polycrystalline diamond material prepared by pressurizing underelevated temperature conditions diamond grains and a binder to form apolycrystalline diamond material comprising 15 percent by volume or lessdiamond grains having a grain size of 20 micrometers or less based onthe total volume of the material.
 2. The polycrystalline diamondmaterial as recited in claim 1 comprising 10 percent by volume or lessdiamond grains having a grain size of 20 micrometers or less based onthe total volume of the material.
 3. The polycrystalline diamondmaterial as recited in claim 1 comprising 5 percent by volume or lessdiamond grains having a grain size of 20 micrometers or less based onthe total volume of the material.
 4. The polycrystalline diamondmaterial as recited in claim 1 wherein diamond grains used to preparethe polycrystalline material comprises 15 percent by volume or lessdiamond grains having a grain size of 20 micrometers or less based onthe total volume of the diamond grains and binder material.
 5. Thepolycrystalline diamond material as recited in claim 1 furthercomprising the step of processing the diamond grains prior topressurizing, wherein during the step of processing the volume percentof diamond grains sized 20 micrometers or less is increased from that ofthe diamond grains used to prepare the material.
 6. The polycrystallinediamond material as recited in claim 1 wherein the binder material isselected from the group consisting of Co, Ni, Fe, and mixtures thereof,and wherein the diamond grains are present in the range of from about 50to 95 percent by volume of the total mixture.
 7. The polycrystallinediamond material as recited in claim 1 wherein a majority of the diamondgrains have a grain size in the range of from about 35 to 60micrometers.
 8. A rotary cone rock bit comprising a bit body includingat least one journal pin extending from a leg portion of the bit, acutter cone rotatably mounted on the journal pin, and an insert disposedalong a surface of the cutter cone, the insert comprising apolycrystalline diamond construction including the polycrystallinediamond material as recited in claim 1 disposed along a working surfaceof the insert.
 9. A polycrystalline diamond material that is preparedby: processing diamond grain starting materials into a desired greenpart, the diamond grain starting materials having a volume percent ofdiamond grains sized 20 micrometers and less that is less than that ofthe diamond grains in the processed green part; and pressurizing underelevated temperature conditions the green part to form thepolycrystalline diamond material, wherein the polycrystalline diamondmaterial comprises greater than about 85 percent by volume diamondgrains sized greater than 20 micrometers.
 10. The polycrystallinediamond material as recited in claim 9 wherein the diamond grainstarting material comprises less than 10 percent by volume diamondgrains sized 20 micrometers or less based on the total volume of thestarting diamond grains.
 11. The polycrystalline diamond material asrecited in claim 9 comprising greater than 90 percent by volume diamondgrains having a grain size of greater than 20 micrometers based on thetotal volume of the material.
 12. An earth-boring drill bit comprising anumber of drill bit inserts attached thereto, the drill bit insertscomprising a polycrystalline diamond material disposed along an insertworking surface, the polycrystalline diamond material comprising greaterthan 85 percent by volume diamond grains sized greater than 20micrometers based on the total volume of the material.
 13. The drill bitas recited in claim 12, wherein the polycrystalline diamond material isprepared by: processing diamond grains into a desired green part,wherein during the processing step the volume percent of diamond grainssized 20 micrometers or less is increased; and pressurizing underelevated temperature conditions the green part to form thepolycrystalline diamond material.
 14. The drill bit as recited in claim13 wherein the diamond grains used to form the green part comprisesbefore processing less than about 10 percent by volume diamond grainssized 20 micrometers or less based on the total volume of the diamondgrains.
 15. The drill bit as recited in claim 13 wherein a major volumeof the diamond grains used to form the green part is sized in the rangeof from 35 to 55 micrometers.
 16. The drill bit as recited in claim 12wherein the polycrystalline diamond material comprises greater than 90percent by volume diamond grains sized greater than 20 micrometers basedon the total volume of the material.
 17. The drill bit as recited inclaim 12 wherein the polycrystalline diamond material comprises up toabout 50 percent by volume binder selected from the group consisting ofCo, Ni, Fe, and mixtures thereof.
 18. The drill bit as recited in claim12 wherein the diamond grains in the polycrystalline diamond materialare present in the range of from about 50 to 95 percent by volume basedon the total volume of the material, and wherein the diamond grainscomprise 10 percent by volume or less diamond grains sized 20 micrometeror less based on the total weight of the material.
 19. The drill bit asrecited in claim 12 wherein the polycrystalline diamond materialcomprises a random arrangement of multiple material phases.
 20. Thedrill bit as recited in claim 12 further comprising: a bit bodyincluding at least one journal pin extending from a leg portion of thebit; and a cutter cone rotatably mounted on the journal pin; wherein thedrill bit inserts are disposed along a surface of the cutter cone.